Method and device for accelerating a motor vehicle

The invention relates to a motor vehicle designed to be operated in a coasting mode. In particular, the invention relates to a method and a corresponding device for accelerating a motor vehicle upon exit from a coasting mode of the vehicle.

A vehicle having an internal combustion engine can be designed to temporarily decouple the internal combustion engine from the drivetrain of the vehicle during a journey and possibly deactivate it to reduce the energy consumption of the vehicle. In other words, the vehicle can be designed to be temporarily operated in the coasting mode during a journey.

The present document relates to the technical problem of enabling a particularly comfortable coasting mode of a vehicle in an efficient manner, in particular in conjunction with a distance and/or speed control function of the vehicle.

The object is achieved by each of the independent claims. Advantageous embodiments are described, inter alia, in the dependent claims. It is to be noted that additional features of a claim dependent on an independent claim, without the features of the independent claim or in combination with only a subset of the features of the independent claim, can form a separate invention independent of the combination of all features of the independent claim, which can be made the subject matter of an independent claim, a divisional application, or a subsequent application. This applies in the same manner to technical teachings described in the description which can form an invention independent of the features of the independent claims.

According to one aspect, a (control) device for controlling the coasting mode of a (motor) vehicle in the context of a distance and/or speed control function of the vehicle is described. During the operation of the distance and/or speed control function, the driving speed can be adapted automatically in dependence on a target distance (defined by the driver) to the preceding vehicle driving (directly) in front of the vehicle and/or (during a free drive) in dependence on a target speed (defined by the driver), in particular controlled (to the target distance and/or to the target speed).

The device can be configured to decouple the drive motor (in particular the internal combustion engine) of the vehicle from the drivetrain of the vehicle (and possibly to deactivate the drive motor) in order to start the coasting mode. Alternatively or additionally, the device can be configured to couple the drive motor with the drivetrain of the vehicle (and possibly to activate the drive motor) in order to end the coasting mode. The vehicle can roll in the coasting mode without action of a drive torque and/or a drag torque of the drive motor.

During the coasting mode of the vehicle, typically no drive torque is therefore caused by the drive motor of the vehicle. No braking torque (due to one or more friction brakes of the vehicle) can possibly also be effectuated during the coasting mode. Therefore, possibly no active distance and/or speed control function can take place during the coasting mode. However, it can be monitored in this case that during the coasting mode the distance of the vehicle to the preceding vehicle remains within a predefined tolerance band around the target distance and/or that the driving speed of the vehicle remains within a predefined tolerance band around the target speed. An active distance and/or speed control function (to the target distance or to the target speed) can take place outside the coasting mode. In particular, in this case it is possible to cause the distance and/or the driving speed to be adjusted to the target distance or to the target speed directly after ending the coasting mode.

The device is configured to determine that the vehicle, upon exit from the coasting mode (in particular at the exit driving progression of the exit from the coasting mode), has an actual driving speed which is below the target speed of the distance and/or speed control function (for example, by 5% or more, or by 10% or more), and/or has an actual distance to a preceding vehicle, which is above the target distance of the distance and/or speed control function (for example, by 5% or more, or by 10% or more). This can be ascertained on the basis of sensor data from one or more surroundings sensors (for example, from a radar sensor) and/or from one or more status sensors (for example, from a speed sensor).

It can therefore be detected that the vehicle, upon exit from the coasting mode, has an excessively low driving speed and/or an excessively high distance for the distance and/or speed control function. In such a situation, a standard acceleration can be effectuated in a case without reference to the coasting mode in the context of the distance and/or speed control function.

In particular, the device can be configured to repeatedly detect in the context of the distance and/or speed control function (if no coasting exit has taken place within a specific preceding period of time or within a specific preceding driving distance) that the actual speed is below the target speed and/or that the actual distance is above the target distance. The standard acceleration can then be effectuated in reaction thereto in order to adjust, in particular control, the actual speed to the target speed and/or the actual distance to the target distance. In the distance and/or speed control function, a standard acceleration can therefore be effectuated as a standard measure in order to keep the vehicle at the target speed and/or at the target distance.

The standard acceleration effectuated in the context of the distance and/or speed control function can depend on the extent of the deviation (i.e., the difference) between the actual speed and the target speed and/or between the actual distance and the target distance.

The device can be configured to repeatedly ascertain the difference between the actual speed and the target speed and/or between the actual distance and the target distance in the context of the distance and/or speed control function (if no coasting exit has taken place within a specific preceding period of time or within a specific preceding driving distance). The value of the standard acceleration can then be ascertained in dependence on the respective difference, in particular using a predefined and/or stored relationship between the value of the standard acceleration and the difference. The value of the standard acceleration typically increases with increasing difference value. A particularly reliable distance and/or speed control function can thus be effectuated.

The device can be configured (deviating from the standard mode of the distance and/or speed control function), upon an exit from the coasting mode, to effectuate a coasting exit acceleration of the vehicle reduced in relation to the standard acceleration of the distance and/or speed control function, in order to approximate the actual speed to the target speed and/or to approximate the actual distance to the target distance. The coasting exit acceleration can be 10% or more, in particular 20% or more, below the standard acceleration.

The device can be configured in particular to effectuate the (reduced) coasting exit acceleration of the vehicle for a predefined driving progression range directly following the exit from the coasting mode. The standard acceleration of the distance and/or speed control function can then be effectuated subsequently to the predefined driving progression range. The driving progression range can be a specific period of time (for example, of 1 second or more, and/or of 10 seconds or less) after the exit time of the exit from the coasting mode. Alternatively or additionally, the driving progression range can be a specific driving distance (for example, 10 m or more, and/or 100 m or less), after the exit position of the exit from the coasting mode.

As described above, the value of the standard acceleration can be dependent on the difference between the actual speed and the target speed and/or on the difference between the actual distance and the target distance. In a corresponding manner, the value of the coasting exit acceleration can also be dependent on the difference between the actual speed and the target speed and/or on the difference between the actual distance and the target distance. The device can be configured, in the driving progression range (directly) following the exit from the coasting mode, to effectuate a coasting exit acceleration having a value which is less than the respective value of the standard acceleration (for example is less, by 10% or more, in particular 20% or more, than the respective value of the standard acceleration) at least for a part of the driving progression range or for the entire driving progression range.

A device is therefore described which is configured, in the context of the distance and/or speed control function, to selectively effectuate a coasting exit acceleration reduced in relation to the standard acceleration upon a coasting exit. The comfort of the distance and/or speed control function can thus be increased in an efficient manner.

The coasting exit acceleration effectuated by the device can be designed such that the actual driving speed directly following the exit from the coasting mode, in particular for the (entire) predefined driving progression range directly following the exit from the coasting mode, essentially has no jerk. The jerk typically corresponds to the second (time) derivative of the driving speed of the vehicle. The coasting exit acceleration can be such that the jerk is less an absolute value than a predefined jerk threshold value (within the entire driving progression range). The jerk threshold value can be below the perceptibility limit for a human.

The device can be configured in particular to ascertain the profile of the actual driving speed of the vehicle in a specific (temporal and/or distance) range before and/or at the exit driving progression, at which the exit from the coasting mode takes place.

The coasting exit acceleration can then be ascertained in dependence on the ascertained profile of the actual driving speed of the vehicle, in particular such that the actual driving speed of the vehicle (directly) following the exit driving progression (possibly for the entire predefined driving progression range) has substantially no jerk (for example, in absolute value is below the jerk threshold value).

A particularly comfortable distance and/or speed control function can be effectuated by effectuating a jerk-free acceleration following a coasting exit.

The device can be configured to predict a distance and/or speed profile of the vehicle in the coasting mode proceeding from a current driving progression of the vehicle (e.g., proceeding from the current time and/or proceeding from the current position). The predicted distance and/or speed profile can indicate the temporal and/or spatial distance of the vehicle to the preceding vehicle driving (directly) in front of the vehicle and/or the driving speed of the vehicle as a function of the driving progression (proceeding from the current driving progression). The predicted distance and/or speed profile can extend here proceeding from the current driving progression over a predefined prediction horizon.

The driving progression can indicate the position of the vehicle along the roadway traveled by the vehicle or correspond thereto. Alternatively or additionally, the driving progression can indicate the respective point in time during the journey of the vehicle or correspond thereto. The prediction horizon can therefore correspond to a specific distance and/or time horizon (e.g., 100 m or more, or 500 m or more; or 10 seconds or more, or 20 seconds or more).

The device can be configured to ascertain an upcoming gradient profile of the roadway traveled by the vehicle (for the prediction horizon). This information can be ascertained on the basis of a digital map for the roadway network traveled by the vehicle. The distance and/or speed profile of the vehicle in the coasting mode can then be predicted in a precise manner on the basis of the upcoming gradient profile.

The device can furthermore be configured to ascertain status data with respect to the status (e.g., the current driving speed) of the vehicle and/or with respect to the status (e.g., the current driving speed) of the preceding vehicle driving in front of the vehicle. The distance and/or speed profile of the vehicle in the coasting mode can then be predicted in a particularly precise manner on the basis of the status data.

Upon the prediction of the distance and/or speed profile of the vehicle, it can be assumed that the vehicle is in the coasting mode during the entire prediction horizon. Furthermore, an assumption with respect to the behavior of the preceding vehicle during the prediction horizon can be made. For example, it can be assumed that the driving speed of the preceding vehicle remains constant during the entire prediction horizon.

The device is furthermore configured to compare the predicted distance and/or speed profile of the vehicle to the target distance or to a distance threshold value lying above the target distance. Alternatively or additionally, the device can be configured to compare the predicted distance and/or speed profile to the target speed or to a speed threshold value of the distance and/or speed control function of the vehicle lying below the target speed. The following can be ascertained in the scope of the method, for example:

The coasting mode can then be controlled in dependence on the comparison (in particular in dependence on the ascertained driving progression section and/or in dependence on the ascertained driving progression), in particular can be started or ended. A particularly energy-efficient and comfortable coasting mode of a vehicle having active distance and/or speed control function can thus be effectuated. During the distance and/or speed control function and/or during the coasting mode, it is possible to deviate here at least temporarily and/or within a specific tolerance band from the target distance and/or from the target speed. The tolerance band or the respective threshold value can be, for example, ±5% or less or ±10% or less of the target distance or the target speed.

According to a further aspect, a (road) motor vehicle (in particular a passenger vehicle or a truck or a bus or a motorcycle) is described which comprises the (control) device described in this document.

According to a further aspect, a method for controlling the coasting mode of a vehicle in the context of a distance and/or speed control function of the vehicle is described. The method comprises determining that the vehicle, upon exit from the coasting mode, has an actual driving speed which is below the target speed of the distance and/or speed control function, and/or has an actual distance to the preceding vehicle which is above the target distance of the distance and/or speed control function. The method furthermore comprises, in reaction thereto, effectuating a coasting exit acceleration of the vehicle reduced in relation to a standard acceleration of the distance and/or speed control function, in order to approximate the actual speed to the target speed and/or in order to approximate the actual distance to the target distance.

According to a further aspect, a software (SW) program is described. The SW program can be configured to be executed on a processor (e.g., a control unit of a vehicle), and in order to thus carry out the method described in this document.

According to a further aspect, a storage medium is described. The storage medium can comprise an SW program which is configured to be executed on a processor and to thus carry out the method described in this document.

It is to be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspects of the methods, devices, and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways. Furthermore, features set forth between parentheses are to be understood as optional features.

The invention will be described in more detail hereinafter on the basis of exemplary embodiments. In the figures

As described at the outset, the present document relates to increasing the comfort of the coasting mode of a motor vehicle. In this context,shows an exemplary vehicle. The vehiclecomprises one or more surroundings sensors(e.g., at least one camera, a radar sensor, a lidar sensor, and/or an ultrasonic sensor), which are configured to acquire surroundings data (i.e., sensor data) with respect to the surroundings of the vehicle. Furthermore, the vehiclecomprises one or more vehicle sensors, which are configured to acquire status data (i.e., sensor data) with respect to a status (for example, with respect to the driving speed) of the vehicle.

A (control) deviceof the vehiclecan be configured to operate the drive motor(in particular the internal combustion engine) of the vehiclein dependence on the surroundings data and/or the status data in order to longitudinally guide the vehiclein an at least partially automated manner. In particular an automatic distance and/or speed control function (in particular ACC, adaptive cruise control) can be effectuated here, in which the driving speed of the vehicleis adjusted automatically in order to adjust the distance of the vehicleto a preceding vehicle driving directly in front of the vehicleto a target distance (which was defined by the driver of the vehicle, for example) and/or to adjust the driving speed of the vehicleduring a free drive (without preceding vehicle) to a target speed (which was defined by the driver of the vehicle, for example).

shows an exemplary driving situation in which the vehicledrives on a roadwaybehind a preceding vehicle. The distancebetween the vehicleand the preceding vehicleis set by the deviceof the vehicleto a specific target distance. The distancecan be a spatial distance here, which corresponds to the spatial distance (for example, measured in meters) between the vehicleand the preceding vehicle. Alternatively or additionally, the distancecan be a temporal distance, which corresponds to the time the vehiclewould require at the current driving speed in order to reach the preceding vehicle(under the assumption that the preceding vehicleis stationary). The temporal distance can correspond, for example, to the quotient of the current driving speed of the vehicleand the spatial distance between the vehicleand the preceding vehicle.

The (control) devicecan be configured to operate the vehicleat least temporarily in a so-called coasting mode during an active distance and/or speed control function. For this purpose, the couplingof the vehiclecan be prompted to decouple the drive motorfrom the drivetrain of the vehicle, in particular from the one or more driven wheels of the vehicle. Furthermore, a deactivation and/or a setting aside of the drive motorcan be effectuated. The vehiclethen rolls (without drag torque and/or without drive torque of the drive motor) over the roadwaytraveled by the vehicle. The energy consumption of the vehiclecan thus be reduced.

The vehiclecan comprise a position sensorwhich is configured to acquire position data (i.e., sensor data) with respect to the respective current position of the vehicle. The position data can comprise, for example, coordinates of a global navigation satellite system (GNSS), such as GPS coordinates. The devicecan be configured to ascertain the spatial profile of the roadway, on which the vehicleis being driven, on the basis of the position data and on the basis of a digital map with respect to the roadway network traveled by the vehicle. A driving route through the roadway network can optionally have been planned by means of a navigation system of the vehicle. It can be recognized on the basis of the driving route along which roadwaythe vehiclewill be driven proceeding from the current time and/or proceeding from the current position. Furthermore, the spatial profile, in particular the gradient profile, of the upcoming roadwaycan be ascertained on the basis of the digital map.

shows an exemplary gradient profileof the roadwaytraveled by the vehicle. The gradient profileindicates the gradientof the roadwayas a function of the position on the roadwayand/or as a function of the time during a journey (in general as a function of the driving progression of the vehicle).

The devicecan be configured to predict a distance profile and/or a speed profile of the vehiclein the coasting mode on the basis of the gradient profileof the upcoming roadway. The distance profile can indicate the (temporal and/or spatial) distanceof the vehicleto the preceding vehicle, as a function of the position and/or as a function of the time (in general as a function of the driving progression). The speed profile can indicate the driving speed of the vehicleas a function of the position and/or as a function of the time (in general as a function of the driving progression). It can be assumed here that the vehicleis operated in the coasting mode (without action of a drive and/or braking torque generated by the vehicle). Furthermore, (to ascertain the distance profile), a specific speed behavior of the preceding vehiclecan be assumed; for example, it can be assumed that the preceding vehicleis driven at a constant driving speed. The distance profile and/or the speed profile can be predicted, for example, for a spatial prediction horizon of 50 m or more, or of 100 m or more (proceeding from the current position of the vehicle) and/or for a temporal prediction horizon of 5 seconds or more, or of 10 seconds or more.

The activation (also referred to as the entry) and/or the deactivation (also referred to as the exit) of the coasting mode of the vehiclecan then be carried out in a precise and energy-efficient manner (during use of the distance and/or speed control function) in dependence on the predicted distance profile and/or in dependence on the predicted speed profile. In particular, the deviceof the vehiclecan be configured (during the operation of the distance and/or speed control function) to predict a distance profile and/or a speed profile of the vehiclein the coasting mode proceeding from the current position of the vehicleand/or proceeding from the current time (in general proceeding from the current driving progression). An entry into or an exit out of the coasting mode can then be effectuated in dependence on the predicted distance profile and/or speed profile.

The devicecan be configured to effectuate a standard acceleration during the operation of the distance and/or speed control function if it is detected that the actual distanceis greater than the target distance and/or that the actual driving speed is less than the target speed. Standard acceleration can have a specific standard acceleration value with which the vehicleis accelerated. The acceleration can be effectuated by the drive motorof the vehicle.

shows an exemplary predicted distance and/or speed profileduring the coasting mode of the vehicle. As already described, the distance and/or speed profileindicates the actual distance and/or the actual speedof the vehicleas a function of the driving progression(for example, the position and/or the time) during the journey of the vehicle.

furthermore shows an exemplary tolerance bandaround the target distance and/or around the target speed, having a lower threshold valueand an upper threshold value, which includes the target distance and/or the target speed. In, in particular a tolerance bandis shown around the target speed(for a speed control function after exit from the coasting mode). The aspects described in this document are applicable accordingly for a distance control function after exiting from the coasting mode.

The devicecan be configured to determine on the basis of the predicted distance and/or speed profilethat the predicted distance and/or speed profilewill intersect a threshold value,of the tolerance bandat an intersection driving progression(in particular the lower threshold valueof the speed tolerance bandand/or the upper threshold valueof the distance tolerance band).

The devicecan furthermore be configured to effectuate an exit from the coasting mode at an exit driving progressionwhich is before the intersection driving progressionby a specific offset value. The vehiclecan have an actual driving speedat the exit driving progression, which lies below the target speed(and/or can have an actual distancewhich lies above the target distance).

The devicecan be configured to effectuate an acceleration of the vehicle(immediately) after the exit from the coasting mode in the context of the distance and/or speed control function, in order to accelerate the vehicleto the target speedand/or in order to cause the vehicleto have the target distance. The standard acceleration of the distance and/or speed control function can be applied here, by which the speed profileshown inis effectuated.

The effectuation of a relatively high standard acceleration following the coasting mode can be perceived as uncomfortable by a user of the vehicle. In particular, a jerk perceived as unpleasant can be caused by the standard acceleration.

The devicecan be configured, following the coasting mode in the context of the distance and/or speed control function, to effectuate a coasting exit acceleration reduced in relation to the standard acceleration so that, for example, the speed profile (or distance profile)shown inresults. In particular, a coasting exit acceleration can be effectuated by which a (noticeable) jerk of the vehicleis avoided. The coasting exit acceleration can in particular be such that during the coasting exit and in a specific phase (i.e., in a specific driving progression range), which directly follows the coasting exit, the second derivative of the driving speed of the vehicleis substantially zero. A particularly comfortable coasting exit can thus be effectuated.

At the end of the coasting process, the actual driving speedof the vehiclecan be at the lower endof the tolerance band(for example, due to incorrect mapping and/or due to an incorrect prediction of the distance and/or speed profile). As a result thereof, it is necessary to accelerate back to the set speedof the longitudinal guidance after ending the coasting process. A regular acceleration process using the standard acceleration can result in a noticeable jerk, which can be perceived by a user of the vehicleand/or can make the user aware of the coasting process (so that the coasting process is no longer embedded unnoticed in the driving mode of the vehicle).